The present invention relates to a pusher device for positioning the ends of plastic optical fibers, and more particularly to a pusher device employable for a multiple-core optical fiber cable incorporating plural plastic optical fibers.
FIG. 3 shows a perspective view of an end portion of a dual-core optical fiber cable in the prior art. As shown in FIG. 3, an optical fiber cable 1 is constituted of two plastic optical fibers 2 and 3 having different flows, sheaths 4 and 5 made of polyethylene, etc. for covering the respective optical fibers 2 and 3, and an outer cover 6 made of polyvinyl-chloride, etc. for generally covering the sheaths 4 and 5. The sheaths 4 and 5 are exposed at the end portion of the optical fiber cable 1, and are held by a pusher device (not shown) to enhance a frictional force between the optical fiber 2 and the sheath 4 and a frictional force between the optical fiber 3 and the sheath 5, thus positioning the ends of the optical fibers 2 and 3. The optical fibers 2 and 3 are projected from the end surfaces of the sheaths 4 and 5 by a predetermined amount. The end surfaces 2a and 3a of the optical fibers 2 and 3 are arranged in opposed relation with an optical connector (not shown) so as to transmit an optical signal.
However, in the conventional pusher device, the end portions of the sheaths 4 and 5 are only held by a predetermined clamping force. Therefore, when a tensile force is applied near the end portion of the optical fiber cable 1, the end portions of the optical fibers 2 and 3 are also pulled to easily generate slippage of the end surfaces 2a and 3a. In order to prevent a bad influence of the tensile force to the end portions of the optical fibers 2 and 3, it may be proposed that the end portion of the outer cover 6 is fixed to the pusher device. In this case, when the optical fiber cable 1 is bent near its end portion as shown in FIG. 3, the end surfaces 2a and 3a of the optical fibers 2 and 3 are slipped from a predetermined position because of difference in curvature. For example, the optical fiber 2 on the side of smaller curvature in FIG. 3 is projected from the predetermined position, and is brought into abutment against the optical connector (not shown) to cause a serious accident such as damage of the end surfaces.
On the other hand, if the clamping force of the pusher device is increased to intensively hold the end portions of the optical fibers 2 and 3, so as to prevent the bad influence due to the tensile force and the bending, there will be generated local stress concentration to remarkably reduce light transmittance.